Flat ribbon cables have been used extensively when it is necessary to interconnect different types of electronic machines, such as computers and peripheral equipment, or to cable connect internal portions of machines such as in computers. Although advantageous in many respects, flat ribbon cables, present a particular signal assignment or conductor assignment pattern at their ends. The signal assignment or conductor assignment, being the designation of particular conductors for particular signals in a typically left to right pattern across the end of the flat ribbon cable, is not always the same for all pieces of equipment or all interfaces that are being interconnected.
When the signal assignment pattern varies from connection to connection, and hence from one end of the cable to the other in order to be compatible with both pieces of equipment or both interfaces being interconnected, it is necessary to reroute the conductors at some point between the ends of the cables.
It is particularly difficult to accomplish this with flat ribbon cables inasmuch as it takes a reasonably high degree of skill to separate adjacent conductors without damaging them and, at the same time to reroute one or more of the conductors to a different position relative to the other conductors of the cable. With ribbon cables typically having a center to center distance between adjacent conductors of 0.050 inches or less, and the connectors to which the cables are terminated having similar adjacent spacing between contacts, the customized connection and soldering of rerouted conductors becomes a very labor intensive operation.
Efforts have been made in the past to overcome this problem and are probably best represented by U.S. Pat. No. 4,418,239 to Larson, et. al. The Larson, et. al. patent discloses a technique for rerouting conductors to shift at least one conductor and, more particularly the signal on that conductor, to a different relative position at some point between the ends of the cable.
The Larson, et. al. technique involves applying an insulative patch over the conductors on the cable substrate and then depositing an electrically conductive path between the termination points of conductors on the cable substrate and on top of the insulating patch to connect the segments of the conductors on the cable substrate. Where it is necessary for the deposited electrically conductive path on the insulating patch to cross over another electrically conductive path, multiple insulating patches are laid down to separate the conductive paths, preventing shorting. The Larson, et. al. technique requires the ability not only-to position accurately a conductive patch having holes at appropriate locations, but also to deposit and to cure silk screenable electrically conductive paste to form the conductive paths and equipment necessary to cure or to dry the silk screenable paste. While this technique does in fact rearrange the signal pattern from one end of the cable to the other end of the cable, it does not permit the easy customization of a cable as required at a particular installation site or as required on the assembly line.
Other solutions to this type of problem have included the inclusion of a circuit and an integrated circuit timer to control the reassignment of signals between the ends of a cable. Such is illustrated in U.S. Pat. No. 4,607,170 to Wickman, and the use of a bank of switches and switching gear such as illustrated in U.S. Pat. No. 4,579,407 to Shimada.
Both of these solutions are not only expensive, but require substantial additional equipment be interconnected into or included within the cable run.
Without the ability to reassign the signal pattern on the conductors at the end of the cables easily and economically, a large number of different and unique cables must be stocked to accommodate all of the desired combinations of signal assignment that may be necessary for the manufacture, repair or maintenance, and interconnection of different electronic devices.